U.S. patent number 5,030,900 [Application Number 07/397,444] was granted by the patent office on 1991-07-09 for spindle orientation control apparatus.
This patent grant is currently assigned to Fanuc Ltd.. Invention is credited to Shinichi Kono, Hironobu Takahashi.
United States Patent |
5,030,900 |
Kono , et al. |
July 9, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Spindle orientation control apparatus
Abstract
A spindle orientation control apparatus according to the
invention provides a spindle (4) for which a magnetic sensor senses
the spindle and outputs stopping-position proximity (LS) signal and
a stopping position determination (MS). The spindle (4) is coupled
via gear or belt (5) to a spindle motor (2) wherein the spindle is
controlled to stop at a fixed position based on a velocity command
conforming to velocity of the spindle motor (4). Velocity pulses
for detecting the rotational velocity of the motor can be employed
as position pulses. A velocity command value (VCMD) can be reduced
by an amount corresponding to a number of fed back velocity pulses
a. The velocity value is clamped at a predetermined level when the
velocity command value of the spindle attains a predetermined level
until a final changeover. The final the spindle changeover for
making equal stop-position decision signal (MS) signal and the
velocity command value when an edge of the stop-position proximity
signal (LS) signal is detected. Monitoring of position from
velocity pulses can also be performed also at velocities less than
an orientation velocity, and a second orientation velocity can be
determined after the introduction of power. This makes it possible
to stop the spindle at a fixed position in a short period of
time.
Inventors: |
Kono; Shinichi (Oshino,
JP), Takahashi; Hironobu (Oshino, JP) |
Assignee: |
Fanuc Ltd. (Minamitsuru,
JP)
|
Family
ID: |
18285199 |
Appl.
No.: |
07/397,444 |
Filed: |
August 14, 1989 |
PCT
Filed: |
December 28, 1988 |
PCT No.: |
PCT/JP88/01341 |
371
Date: |
August 14, 1989 |
102(e)
Date: |
August 14, 1989 |
PCT
Pub. No.: |
WO89/06394 |
PCT
Pub. Date: |
July 13, 1989 |
Foreign Application Priority Data
|
|
|
|
|
Dec 28, 1987 [JP] |
|
|
62-335139 |
|
Current U.S.
Class: |
318/592; 318/569;
324/207.22; 318/561; 318/653 |
Current CPC
Class: |
G05B
19/39 (20130101); G05B 19/237 (20130101); G05B
2219/41007 (20130101); G05B 2219/42114 (20130101); G05B
2219/42104 (20130101); G05B 2219/43127 (20130101); G05B
2219/43194 (20130101); G05B 2219/42215 (20130101); G05B
2219/42203 (20130101) |
Current International
Class: |
G05B
19/19 (20060101); G05B 19/23 (20060101); G05B
19/39 (20060101); G05B 011/18 () |
Field of
Search: |
;318/592,561,569,653
;324/207.22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shoop, Jr.; William M.
Assistant Examiner: Bergmann; Saul M.
Attorney, Agent or Firm: Staas & Halsey
Claims
We claim:
1. A spindle orientation control apparatus in which a spindle, from
which a stopping-position proximity signal and a stopping position
determining signal are extracted, is rotatively coupled via a
coupling unit to a spindle motor, from which velocity pulses are
obtained, said spindle orientation control apparatus controlling
the spindle to stop at a fixed position based on a velocity
command, said spindle orientation control apparatus comprising:
setting means for setting a position gain of said spindle;
arithmetic means for determining a first orientation velocity based
on a position gain and a gear ratio of the coupling unit, for
determining a second orientation velocity based on at least a
position gain, and for normalizing the stopping position
determining signal such that a peak level of the stopping position
determining signal is equal to the second orientation velocity;
status sensing and setting means for setting a sequence status
signal according to relative levels obtained by sensing said second
orientation velocity and the velocity pulses fed back from the
spindle motor;
velocity command means for latching the velocity pulses based on
the sequence status signal and reducing the velocity command in
dependence upon the velocity pulses fed back from the spindle
motor; and
control means for outputting the velocity command at a level equal
to the level of the stopping position determining signal when an
edge of the stopping position proximity signal is detected, thereby
performing a fixed-position stop-control by the stopping position
determination signal.
2. A spindle movement control system providing control of a motor
rotatively connected by a transmission to a spindle, said system
comprising:
a velocity detector to output velocity pulses based on the movement
of the motor;
a spindle sensor to sense the position of the spindle and output a
stopping position determining signal and a stopping position
proximity signal;
an arithmetic circuit to output a commanded velocity for control of
the motor, said arithmetic circuit including
means for determining a first orientation velocity based on a
position gain and a transmission ratio of the transmission;
means for determining a second orientation velocity based on at
least a position gain;
means for normalizing the stopping position determining signal such
that a peak level of the stopping position determining signal is
equal to the second orientation velocity;
means for setting states of a plurality of sequence status signals
based on an actual velocity of the motor in relation to the
stopping position proximity signal, the first orientation velocity
and the second orientation velocity; and
means for determining the commanded velocity based on the state of
the sequence status signals and at least one of the velocity
pulses, the stopping position determining signal, the stopping
position proximity signal, the first orientation velocity and the
second orientation velocity; and
a controller, including an amplifier, for controlling said motor
based on the commanded velocity output by said arithmetic
circuit.
3. A control system according to claim 2, wherein said controller
further includes a feedback control loop.
4. A control system according to claim 2, wherein said spindle
sensor is a magnetic sensor having a magnetic sensor head.
5. A control system according to claim 2, wherein the transmission
ratio of the transmission is a gear ratio.
6. A control system according to claim 2, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state.
7. A control system according to claim 2, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state and the
actual velocity of the motor is below the second orientation
velocity.
8. A control system according to claim 2, wherein said means for
determining the commanded velocity begins decrementing the
commanded velocity by the velocity pulses output from the velocity
detector when the stopping position proximity signal changes
state.
9. A control system according to claim 2, wherein said means for
determining the commanded velocity begins decrementing the
commanded velocity by the velocity pulses output from the velocity
detector when the stopping position proximity signal changes state
until the actual velocity of the motor is below the second
orientation velocity.
10. A control system according to claim 8, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the sequence status signals indicate the stopping position
proximity signal changes state a second time.
11. A control system according to claim 8, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the sequence status signals indicate the stopping position
proximity signal changes state a second time and the actual
velocity of the motor is below the second orientation velocity.
12. A spindle movement control method providing control of a motor
rotatively connected by a transmission to a spindle, said method
comprising the steps of:
(a) outputting velocity pulses based on the movement of the
motor;
(b) sensing the position of the spindle and outputting a stopping
position determining signal and a stopping position proximity
signal;
(c) determining a first orientation velocity based on a position
gain and a transmission ratio of said transmission;
(d) determining a second orientation velocity based on at least a
position gain;
(e) normalizing the stopping position determining signal such that
a peak level of the stopping position determining signal is equal
to the second orientation velocity;
(f) setting states of a plurality of sequence statuses based on an
actual velocity of the motor in relation to the stopping position
proximity signal, the first orientation velocity and the second
orientation velocity;
(g) determining a commanded velocity based on the state of the
sequence statuses and at least one of the velocity pulses, the
stopping position determining signal, the stopping position
proximity signal, the first orientation velocity and the second
orientation velocity; and
(h) controlling the motor based on the commanded velocity.
13. A method according to claim 12, wherein said controlling of the
motor in step (g) further includes the step of providing feedback
control.
14. A method according to claim 12, wherein said determining of
step (c) produces the first orientation velocity based in part on
the transmission ratio of the transmission which is a gear
ratio.
15. A method according to claim 12, wherein said determining of the
commanded velocity in step (f) produces the commanded velocity with
a value indicative of the stopping position determining signal when
the stopping position proximity signal changes state.
16. A method according to claim 12, wherein said determining of the
commanded velocity in step (f) produces the commanded velocity with
a value indicative of the stopping position determining signal when
the stopping position proximity signal changes state and the actual
velocity of said motor is below the second orientation
velocity.
17. A method according to claim 12, wherein said determining of the
commanded velocity in step (f) begins decrementing the commanded
velocity by the velocity pulses when the stopping position
proximity signal changes state.
18. A method according to claim 17, wherein said determining of the
commanded velocity in step (f) outputs the commanded velocity with
a value indicative of the stopping position determining signal when
the sequence statuses indicate the stopping position proximity
signal changes state a second time.
19. A method according to claim 12, wherein said determining of the
commanded velocity in step (f) begins decrementing the commanded
velocity by the velocity pulses when the stopping position
proximity signal changes state until the actual velocity of the
motor is below the second orientation velocity.
20. A method according to claim 19, wherein said determining of the
commanded velocity in step (f) outputs the commanded velocity with
a value indicative of the stopping position determining signal when
the sequence statuses indicate the stopping position proximity
signal changes state a second time and the actual velocity of the
motor is below the second orientation velocity.
21. A spindle movement control system providing control of a motor
rotatively connected to a spindle, said system comprising:
a velocity detector to output an actual velocity based on movement
of the motor;
a spindle sensor to sense the position of the spindle and output a
stopping position determining signal and a stopping position
proximity signal;
an arithmetic circuit to output a commanded velocity for control of
the motor, said arithmetic circuit including
means for determining a first orientation velocity based on at
least a position gain;
means for determining a second orientation velocity based on at
least position gain;
means for normalizing the stopping position determining signal such
that a peak level of the stopping position determining signal is
equal to the second orientation velocity; and
means for determining the commanded velocity based on at least one
of the actual velocity, the stopping position determining signal,
the stopping position proximity signal, and the second orientation
velocity; and
a controller for controlling said motor based on the commanded
velocity output by said arithmetic circuit.
22. A control system according to claim 21, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state.
23. A control system according to claim 21, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state and the
actual velocity of the motor is below the second orientation
velocity.
24. A control system according to claim 21, wherein said means for
determining the commanded velocity begins decrementing the
commanded velocity by the velocity pulses output from the velocity
detector when the stopping position proximity signal changes
state.
25. A control system according to claim 21, wherein said means for
determining the commanded velocity begins decrementing the
commanded velocity by the velocity pulses output from the velocity
detector when the stopping position proximity signal changes state
until the actual velocity of the motor is below the second
orientation velocity.
26. A control system according to claim 24, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state a second
time.
27. A control system according to claim 24, wherein said means for
determining the commanded velocity outputs the commanded velocity
with a value indicative of the stopping position determining signal
when the stopping position proximity signal changes state a second
time and the actual velocity of the motor is below the second
orientation velocity.
Description
TECHNICAL FIELD
This invention relates to a spindle orientation control apparatus
for controlling a spindle motor to stop the motor at a fixed
position.
BACKGROUND ART
In a numerically controlled (NC) machine tool, it is necessary to
stop a spindle at an arbitrary position with high precision in
accordance with a particular purpose. For example, to carry out
tapping machining at a predetermined rotational angular position on
a workpiece by means of a lathe, it is required that a spindle be
stopped at the predetermined rotational position (this is referred
to as "spindle orientation").
FIG. 6 is a block diagram illustrating a conventional spindle
orientation control apparatus. This spindle orientation control
apparatus is such that a spindle A is coupled via a gear d to a
servomotor M, acting as a spindle motor, with spindle orientation
control being performed by an NC unit a. In FIG. 6, SW denotes a
switch for transmitting a command from the NC unit a to a velocity
control circuit b and a position control circuit c in a switching
fashion. A tachogenerator TG detects an average velocity AV of the
servomotor M. Magnetic sensor S detects the rotatioal position of
the spindle.
The operation of this orientation control apparatus will now be
described with reference to a characteristic diagram of motor
velocity shown in FIG. 7. When stop-control is performed while
detecting the rotating state of the spindle by the magnetic sensor
S, the spindle A is subjected to control at a fixed velocity until
an orientation command (ORCM) is outputted from the NC unit a to
the velocity control circuit b, or position control circuit c, in
accordance with a velocity pattern at the time of orientation
control. The rotational velocity of the motor is controlled by a
velocity command VCMD from the NC unit a when time t.sub.0 arrives,
in response to which the velocity declines at a fixed slope. At
time t.sub.1, the rotational velocity of the servomotor M has
dropped to a predetermined velocity, from which moment onward there
is a transition to rotation at a fixed velocity based on the
commanded orientation velocity. At this time, the contact of switch
SW is changed over so that the connection of NC unit a is changed
from the velocity control circuit b to the position control circuit
c. As a result, the spindle A is controlled in accordance with the
rotational position signal from the magnetic sensor S from time
t.sub.2 onward, so that it is possible to stop the spindle at a
target position.
In this conventional spindle orientation control apparatus, spindle
velocity attains the orientation velocity owing to input of the
velocity AV of servomotor M to the position control circuit c,
after which a signal indicative of one revolution of the spindle A
is detected, based on the orientation command, and fixed
position-stop control becomes possible. This means that the spindle
A can be stopped at the fixed position only upon making at least
one revolution after the spindle has attained the orientation
velocity.
DISCLOSURE OF THE INVENTION
The present invention has been devised in order to solve the
foregoing problem and its object is to provide a spindle
orientation control apparatus in which position is monitored by
velocity pulses at orientation time and at other times as well,
wherein a spindle can be stopped at a fixed position in a short
period of time.
In accordance with the invention, there can be provided a spindle
orientation control apparatus in which a spindle for which there
are extracted a spindle stopping-position proximity (LS) signal and
a stopping position determination (MS) signal is coupled via
coupling means to a spindle motor. The spindle is controlled to
stop at a fixed position based on a velocity command conforming to
velocity of the spindle. The control apparatus comprises setting
means for setting position gain of the spindle, arithmetic means
for deciding a first orientation velocity conforming to the
position gain and a gear ratio of the coupling means, and a second
orientation velocity clamped at a level continuous with the MS
signal. Also, included are status sensing means for deciding a
predetermined sequence status signal from the second orientation
velocity and a velocity pulse fed back as a position pulse,
velocity command means for latching the velocity pulse by the
sequence status pulse and reducing the velocity command in
dependence upon the velocity pulse fed back, and control means for
connecting the velocity command to the MS signal level and
detecting the LS signal, thereby performing fixed-position
stop-control by the MS signal.
Accordingly, the spindle orientation control apparatus of the
invention is such that position is monitored based on velocity
pulses at a velocity less than the first orientation velocity, and
a velocity command corresponding to the second orientation velocity
is decided after power is introduced, so that the spindle can be
stopped at the fixed position in a short period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the simplified construction
of the invention,
FIG. 2 is a view of a magnetic sensor arrangement,
FIG. 3 is a characteristic diagram signal,
FIGS. 4(a)-(e) are explanatory signal diagrams,
FIG. 5 is a flowchart,
FIG. 6 is a block diagram of a conventional example, and
FIG. 7 is a characteristic signal diagram referring to FIG. 6.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the invention will now be described in detail with
reference to the drawings.
FIG. 1 is a block diagram illustrating the simplified construction
of the spindle orientation control apparatus. Shown in FIG. 1 is an
arithmetic circuit 1 which includes a microcomputer and the like, a
spindle motor 2, a velocity detector 3, a spindle 4, a gear or belt
5 connecting the spindle motor to the spindle, a mount 6 for fixing
a magnetic body 8 of a magnetic sensor 7, a magnetic sensor head 9,
amplifiers 10-12, and comparators 13, 14.
A signal detected by the velocity detector 3 is fed into the
arithmetic circuit 1 and comparator 13 as a velocity feedback
signal, and current supplied to the spindle motor is fed back to
the comparator 14 to form a minor loop. A stopping-position
proximity signal LS and a stopping position decision signal MS
enter the arithmetic circuit 1 from the magnetic sensor 7.
As shown in FIG. 2, the magnetic sensor 7 includes a magnetic body
8 of length L (mm) coupled directly to the spindle mount 6, and a
magnetic sensor head 9 arranged at a position a distance H (mm)
from the center of the spindle mount 6.
The operation of the apparatus embodying the invention will be
described with reference to FIG. 3. First, various factors
regarding the invention will be defined.
(a) Each gear ratio of the spindle (Ag) to the spindle motor (Mg)
is Ag:Mg=1:n.
(b) The detection pulses of the velocity detector are np
(pulses/revolution).
(c) The position gain is Gp sec.sup.-1. Here Gp is defined as
Gp=V/.theta., where the amount of motor rotation is .theta. (rad),
when driving the motor in such a manner that a positional offset
becomes zero when the motor is rotated at a fixed velocity V
(rad/sec).
In FIG. 3, a velocity command VCMD is operated on for control when
an orientation command (ORCM) is applied as follows:
In region (1), VCMOR1=60.times.Gp.times.n (rpm) (which is decided
by position gain and gear ratio) is commanded as velocity. At this
time, a sequence status signal SQ.sub.1 is set according to the
relationship between actual velocity TSA and commanded velocity
VCMD. That is, SQ=1 if TSA>VCMD holds, and SQ.sub.1 =1 if
TSA<VCMD holds.
At the changing time to of region (1) .fwdarw. (2), the value of a
velocity pulse counter (provided in the arithmetic circuit) is
latched at the leading edge of the LS signal when the LS signal is
generated.
In region (2), velocity pulses serve as position pulses so that the
velocity command VCMD can be diminished by an amount corresponding
to the fed back velocity pulses. In this region, the velocity
command VCMD is such that a sequence status signal SQ.sub.2 becomes
1. This occurs with velocity between the first orientation velocity
VCMOR1 (as defined above) and a second orientation velocity VCMOR2
(clamped at a level connected with the MS signal as in FIGS. 3 and
4(b)-4(e)).
In region (3) which is a fixed-velocity control region, the
velocity command VCMD attains a level A, which is the second
orientation velocity VCMOR2, where ##EQU1## The command continues
at this level until time t.sub.2, which is the leading edge of the
LS signal. In region (3), the commanded velocity VCMD equals the
second orientation velocity VCMOR2, and a sequence status signal
SQ.sub.3 is set to 1.
In region (4), control is performed by a velocity command based on
the MS signal. Here the peak value of the MS signal meets the value
of the second orientation velocity VCMOR2. In other words, the
stopping position proximity signal MS is normalized such that its
peak value is equal to the magnitude of the level A and stops the
spindle at time t.sub.3, at which the MS signal crosses zero. In
region (4), a sequence status signal SQ.sub.4 becomes 1. If the
sequence status signal SQ.sub.1 =0, orientation is not performed
irrespective of the other sequence status signals.
With the control apparatus of the invention for performing spindle
orientation control by the orientation command ORCM as described
above, it is possible to stop the spindle at a fixed position in a
short period of time by monitoring position, by means of the
velocity detection pulses, both at the time of spindle orientation
and at other times as well.
The foregoing will be described with reference to FIGS. 4(a)-(e) in
conformity with a stop-control pattern, at an initial time t.sub.s,
of a spindle to which the orientation command is applied.
(a) A case where the spindle decelerates and stops within a range
of the LS of a pulse signal is illustrated by FIG. 4(a)
In this case, the MS signal is outputted as a velocity command, and
the spindle is rotated a very small amount and stopped at a
predetermined position.
(b) A case where the spindle decelerates and stops beginning
outside the range of a pulse of the LS signal immediately after
power is introduced is illustrated by FIG. 4(b).
(1) The orientation velocity determined between the position gain
and gear ratio is output from time tb.sub.s to time tb.sub.o.
(2) When the LS signal is detected at time tb.sub.o, the velocity
command is reduced by an amount of fed back velocity pulses.
(3) When the velocity command level A is detected as the same as
the maximum with the MS signal level at time tb.sub.1, there is a
transition to fixed-velocity control.
(4) When the next LS signal rise is detected at time tb.sub.2, the
MS signal level itself becomes the velocity command and the spindle
is stopped at a predetermined position at time tb.sub.3.
(c) A case where the spindle decelerates and stops beginning
outside the range of a pulse the LS signal after having made more
than one revolution is illustrated by FIG. 4(c).
In this case, unlike case (b), there is output a velocity command
VCMOR obtained by subtracting a velocity command decrease
.DELTA.VCMD, produced by the velocity feedback pulse, from the
orientation velocity VCMOR1. If a transition has already been made
to fixed-velocity control of level A when the edge of the first LS
signal is detected, then stop-control is immediately applied.
(d) A case where the spindle begins to decelerates and stop when
the spindle is rotating at a velocity less than the orientation
velocity VCMOR1 outside the range of the LS signal as illustrated
by FIG. 4(d).
In this case also, as in case (c), there is output a velocity
command obtained by subtracting the velocity command decrease
.DELTA.VCMD, produced by the velocity feedback pulse, from the
orientation velocity VCMOR1. If a transition has already been made
to fixed-velocity control of level A when the edge of the first LS
signal is detected, then stop-control is immediately applied.
(e) A case where the spindle begins to decelerate and stop when the
spindle is rotating at a velocity above the orientation velocity
VCMOR1 outside the range of the LS signal as illustrated by FIG.
4(e).
(1) An orientation velocity decided by position gain and gear ratio
is outputted at time te.sub.s. The LS signal at this time has a
narrower pulse interval, as illustrated, because the spindle is
rotating at a high velocity.
(2) When the actual velocity reaches the orientation velocity and
the LS signal is detected at time te.sub.0, the velocity command is
reduced by the amount of feedback of the velocity pulses.
(3) When the level A is detected at time te.sub.1, there is a
transition to fixed-velocity control.
(4) When the next LS signal is detected at time te.sub.2, the MS
signal is changed over as the velocity command and the spindle is
stopped at a predetermined position at time te.sub.3.
FIG. 5 is a flowchart illustrating the processing procedure of the
invention. This flowchart will now be described.
First, at step P1, a check is performed to determine whether the
orientation command ORCM is being output. If the decision rendered
is NO, the sequence status signal SQ.sub.1 is set to 0 at step P2,
and the actual velocity TSA and orientation velocity VCMOR1 are
compared at step P3.
If the decision rendered at step P1 is YES, then the velocity
command VCMD is set to the commanded velocity VCMOR at step P4. At
this time, if the decision of SQ.sub.1 =1 is rendered as YES at
step P5 or the actual velocity TS is found to be smaller than the
velocity command VCMD at step P6, the program proceeds to step P3,
with SQ.sub.1 being set to 1 at step P7. If the actual velocity TSA
is found to be larger than the velocity command VCMD at step 6 or
larger than the orientation velocity VCMOR1 at step 3, then, at
step 12, S.sub.2 -S.sub.4 are set to 0, the position gain Gp.sub.1
is set to Gp, the commanded velocity VCMOR1 is set to the
orientation velocity VCMOR, and the program returns to the first
step P1. Gp.sub.1 is the value of position gain at the time of
orientation.
When it is decided at step P3 that the actual velocity TSA is less
than the orientation velocity VCMOR1, the sequence status signal
SQ.sub.2 is investigated (step P8). If SQ.sub.2 .noteq.1 holds, a
check is performed to determine whether the motor M is rotating
(step 9), a check is performed to determine whether the leading
edge of the LS signal has been detected (step 10), the sequence
status signal SQ.sub.2 is set to 1 (step 11) after edge detection
and the program then proceeds to step 14. When the edge is not
detected, the program proceeds to step P12.
If SQ.sub.2 =1 is found to hold at step P8, the sequence status
signal SQ.sub.3 is checked at step P13. If a NO decision is
rendered at this time, then, at step P14, the level A is set as a
value obtained by subtracting the acceleration command decrease
.DELTA.VCMD, produced by the velocity feedback pulse, from the
orientation velocity VCMOR1; that is, A=VCMOR1-.DELTA.VCMD is set
as the commanded velocity VCMOR. Thereafter, the commanded velocity
VCMOR is compared with the second orientation velocity VCMOR2 (step
P15), and the program returns to the first step P1 as long as VCMOR
does attain VCMOR2. When the commanded velocity VCMOR becomes
smaller than the second orientation velocity VCMOR2, the commanded
velocity VCMOR is set to VCMOR2 and the sequence status signal
SQ.sub.3 is set to 1 (step P16) [this is a state in which a
transition is made to the velocity command VCMOR in the patterns of
FIGS. 4(c), (d)].
When SQ.sub.3 =1 is verified at step P13, it is checked to see
whether SQ.sub.4 =1 holds at step P17. If the decision rendered is
NO, it is checked to see whether the LS signal is 1 (whether the
spindle position is within the range of the LS signal) at step P18.
If the decision rendered is NO, then the second orientation
velocity VCMOR2 is set at the velocity command VCMOR at step P19,
SQ.sub.3, SQ.sub.4 are both made 0, and the program returns to the
initial step P1.
When SQ.sub.4 =1 is verified at step P17, and when the LS signal=1
is verified at step P18, the velocity command VCMOR is set to a
value equal to a predetermined coefficient K times the MS signal
and the sequence status signal SQ.sub.4 is set to 1 at step P20
[this is a state in which a transition is made from fixed-velocity
control to stop-control of level A in the patterns of FIGS. 4(c),
(d)].
Though an embodiment of the present invention has been described,
the invention it not limited thereto but can be modified in various
ways without departing from the scope of the claims.
The spindle orientation control apparatus of the invention is such
that velocity pulses for detecting the rotational velocity of a
motor are employed as position pulses, a velocity command value is
reduced by an amount corresponding to a number of feedback pulses,
the command value is clamped at a predetermined level when the
velocity command value of the spindle attains the predetermined
level, a changeover for making a spindle stop-position decision
signal the velocity command value is performed if a spindle
stop-position proximity signal is detected when the clamped state
prevails, monitoring of position from velocity pulses is performed
also at velocities less than an orientation velocity, and a second
orientation velocity is decided after the introduction of power,
thereby making it possible to stop the spindle at a fixed position
in a short period of time .
* * * * *